Field of the Invention
The present invention generally relates to the area of optical lens and more particularly relates to architecture and designs of optical lens using flat optical lens, where the optical lens is advantageously used in wearable display glasses for various applications including virtual reality augmented reality with 3D capabilities.
Description of the Related Art
Virtual Reality or VR is generally defined as a realistic and immersive simulation of a three-dimensional environment created using interactive software and hardware, and experienced or controlled by movement of the body. A person using virtual reality equipment is typically able to look around the artificially generated three-dimensional environment, moves around in it and interacts with features or items that are depicted on a screen or in goggles. Virtual realities artificially create sensory experiences, which can include sight, touch, hearing, and, less commonly, smell.
Augmented reality (AR) is a technology that layers computer-generated enhancements atop an existing reality in order to make it more meaningful through the ability to interact with it. AR is developed into apps and used on mobile devices to blend digital components into the real world in such a way that they enhance one another, but can also be told apart easily. AR technology is quickly coming into the mainstream. It is used to display score overlays on telecasted sports games and pop out 3D emails, photos or text messages on mobile devices. Leaders of the tech industry are also using AR to do amazing and revolutionary things with holograms and motion activated commands.
The delivery methods of Virtual Reality and Augmented Reality are different when viewed separately. Most 2016-era virtual realities are displayed either on a computer monitor, a projector screen, or with a virtual reality headset (also called head-mounted display or HMD). HMDs typically take the form of head-mounted goggles with a screen in front of the eyes. Virtual Reality actually brings the user into the digital world by cutting off outside stimuli. In this way user is solely focusing on the digital content being displayed in the HMDs. Augmented reality is being used more and more in mobile devices such as laptops, smart phones, and tablets to change how the real world and digital images, graphics intersect and interact.
In reality, it is not always VR vs. AR as they do not always operate independently of one another, and in fact are often blended together to generate an even more immersing experience. For example, haptic feedback, which is the vibration and sensation added to interaction with graphics, is considered an augmentation. However, it is commonly used within a virtual reality setting in order to make the experience more lifelike though touch.
Virtual reality and augmented reality are great examples of experiences and interactions fueled by the desire to become immersed in a simulated land for entertainment and play, or to add a new dimension of interaction between digital devices and the real world. Alone or blended together, they are undoubtedly opening up worlds, both real and virtual alike.
FIG. 1A shows an exemplary goggle now commonly seen in the market for the application of delivering or displaying VR or AR. No matter how a goggle is designed, it appears bulky and heavy, and causes inconvenience when worn on a user. Further most of the goggles cannot be seen through. In other words, when a user wears a goggle, he or she would not be able to see or do anything else. Thus, there is a need for an apparatus that can display the VR and AR but also allows a user to perform other tasks if needed.
Various wearable devices for AR/VR and holographic applications are being developed. FIG. 1B shows a sketch of HoloLens from Microsoft. It weights 579 g (1.2 lbs). With such weight, a wearer won't feel comfortable when wearing it for a period. Indeed, what is available in the market is generally heavy and bulky in comparison to normal glasses. Thus there is a further need for a wearable AR/VR viewing or display device that looks similar to a pair of regular glasses but is also amenable to smaller footprint, enhanced impact performance, lower cost packaging, and easier manufacturing process.
One of the components that make the weight in a goggle is the lenses. Although light materials have been tried, the thickness of the lens or lenses is significant in view of the lenses used in a pair of regular glasses. Thus there is a further need for a lens or lenses that can be made thinner and lighter so that a wearing device for the AR/VR applications could be made lighter or more similar to the regular glasses.
A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or moulded to a desired shape (e.g., to fit into an optical frame). Unlike a prism which refracts light without focusing, a lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. FIG. 2A shows an exemplary compound lens for use in AR/VR glasses. As shown in FIG. 2A, there are at least five individual lenses arranged in line-up along an optical axis. The spaces between the lenses are filled up with air which has a refractive index of 1.0. These individual lenses are of different shapes and made of materials of different refractive indices, arranged one after the other with an optical axis. A single lens is subject to the optical aberrations that can be compensated for to a great extent by using a combination of simple lenses with complementary aberrations, thus the compound lens. It can be appreciated that the compound lens of FIG. 2A, as most lenses in practical uses, are bulky and expensive. As wearable or portable devices are getting smaller in sizes, the lenses for imaging or video are becoming a challenge to fit into such devices. FIG. 2B illustrates the use of a compound lens on iPhone X, where the lens has to stick out from the back of the device because of its relative bulky size of the compound lens in the phone. In addition, the bulky size not only increases the lens cost, it also adds the weight. It would be desirable to have a single lens that achieves what a compound lens may achieve.
Despite tremendous interest in planar lenses in the visible spectrum, there has been no solution that simultaneously satisfies the demands for high numerical aperture (NA) and efficiency, let alone for high end imaging applications. The Capasso Group at Harvard University introduced a breakthrough solution for this problem using titanium dioxide-based metasurfaces that allow the miniaturization of conventional refractive optics into planar structures. The Harvard group shows that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA=0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405 nm (blue), 532 nm (green), and 660 nm (red) with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. However, as admitted by the group, it is still in the research phase, there are no such planar lenses available yet for commercial use.